A coordinated study of the petrology, mineral chemistry, and bulk chemical and isotopic composition of the five ungrouped carbonaceous chondrites Coolidge, Loongana 001, Los Vientos (LoV) 051, Northwest Africa (NWA) 033, and NWA 13400 reveals that these meteorites have a similar set of properties that distinguishes them from the other carbonaceous chondrite groups and allows definition of the new Loongana (CL) group of carbonaceous chondrites. The basic characteristics of the investigated samples are: (1) Lithophile element ratios (e.g., Al/Mg, Si/Mg) are within the typical range of other carbonaceous chondrite groups. (2) Fe-Ni metal abundances are considerably higher than for CV, but similar to CR chondrites. (3) Chondrule size-frequency distributions are similar to CV, but dissimilar to CR chondrites. (4) The mean CAI abundance is ∼1.4 vol%, i.e., lower than in CV but much higher than in CR chondrites. (5) Very low amounts of matrix (17–21 vol%), the lowest among the main carbonaceous chondrite groups (CI, CM, CO, CV, CR, CK). (6) Olivine is nearly equilibrated, with mean fayalite (Fa) values between 12.5 mol% (Loongana 001) and 14.7 mol% (NWA 13400) as a metamorphic effect. (7) Lower Al₂O₃ and higher MgO and Cr₂O₃ concentrations in matrix, compared to matrix in CV, CK, and CR chondrites. (8) Volatile elements (Mn, Na, K, Rb, Cs, Zn, Se, Te, Pb, Tl) are considerably depleted compared to all other main carbonaceous chondrite groups, reflecting the low matrix abundance. (9) Bulk O isotope compositions plot along the CCAM line (Δ¹⁷O −3.96 to −5.47‰), partly overlapping with the CV and CK chondrite fields but including samples that are more ¹⁶O-rich. (10) Unique positions of CL values in the є⁵⁴Cr-є⁵⁰Ti isotope plot, with є⁵⁴Cr values similar to CV, CK, and CO, but є⁵⁰Ti values similar to CR chondrites. All CL chondrites studied here are of petrologic type 3.9 to 4, indicating that they have been thermally metamorphosed on the parent body. The diagnostic features of CL chondrites detailed here provide a basis for identifying CL members of lower petrologic types. Such samples will be important for determining the pristine state of these meteorites and their components.

对五个未分组的碳质球粒陨石柯立芝，Loongana 001，Los Vientos（LoV）051，西北非洲（NWA）033和NWA 13400的岩石学，矿物化学以及大块化学和同位素组成进行的协调研究表明，这些陨石具有以下特征：一组相似的特性，将它们与其他碳质球粒陨石群区分开，并允许定义新的Loongana（CL）碳质球粒陨石群。所研究样品的基本特征是：（1）亲脂元素比例（例如Al / Mg，Si / Mg）在其他碳质球粒陨石基团的典型范围内。（2）Fe-Ni金属丰度比CV高得多，但与CR球粒陨石相似。（3）球粒大小-频率分布与CV相似，但与CR球粒不同。（4）平均CAI丰度约为1.4 vol％，即。例如，低于CV，但远高于CR球粒陨石。（5）基质含量极低（17-21％（体积）），在主要碳质球粒陨石组（CI，CM，CO，CV，CR，CK）中含量最低。（6）橄榄石几乎达到平衡，变质作用的平均铁橄榄石（Fa）值在12.5 mol％（Loongana 001）和14.7 mol％（NWA 13400）之间。（7）下铝与CV，CK和CR球粒陨石中的基质相比，基质中₂ O ₃以及MgO和Cr ₂ O _3的浓度更高。（8）与所有其他主要碳质球粒陨石基团相比，挥发性元素（Mn，Na，K，Rb，Cs，Zn，Se，Te，Pb，Tl）显着减少，反映出较低的基质丰度。（9）堆积氧同位素的组合物沿着所述CCAM线（Δ情节¹⁷ ö-3.96至-5.47‰），部分地与CV和CK陨石字段重叠但包括那些更多的样品¹⁶ O丰富。（10）在єCL值的独特的位置⁵⁴的Cr-є ⁵⁰的Ti同位素情节，与є ⁵⁴ Cr值类似于CV，CK，和CO，但є ⁵⁰Ti值类似于CR球粒陨石。此处研究的所有CL陨石均为岩石学类型3.9至4，表明它们已在母体上热变质。此处详细介绍的CL球粒陨石的诊断特征为识别低岩石类型的CL成员提供了基础。这些样品对于确定这些陨石及其成分的原始状态非常重要。